Question

Interference is possible in (A) light waves only (B) sound waves only (C) both light and Sound waves (D) none of these

Short answer

Interference occurs in both light waves and sound waves, resulting in the superposition of the waves and the formation of constructive or destructive interference. Light waves exhibit interference patterns, such as those seen in Young's double-slit experiment, while sound waves experience changes in loudness due to interference. Therefore, the correct answer is (C) both light and Sound waves.

Step-by-step solution

Understanding Interference

Interference occurs when two or more waves superpose and combine to form a resultant wave with a displacement that is the sum of the displacements of the individual waves. Interference can be constructive, where the resulting wave has a larger amplitude than the original waves, or destructive, where the resulting wave has a smaller amplitude than the original waves.

Interference in Light Waves

Light waves are a type of electromagnetic wave. When two or more coherent light waves interfere, the result is a pattern of bright and dark spots called an interference pattern. This phenomenon is commonly observed in experiments such as Young's double-slit experiment. Therefore, we can conclude that interference is possible in light waves.

Interference in Sound Waves

Sound waves are longitudinal mechanical waves produced by the vibration of particles in a medium, such as air. When two or more sound waves interfere, they can either reinforce each other's amplitudes (constructive interference) or cancel each other's amplitudes (destructive interference). This can cause a change in the loudness of the sound, and the effect is often heard in everyday experiences, for example, when different speakers play sound simultaneously. Therefore, it is clear that interference is possible in sound waves as well.

Conclusion

Based on the understanding of interference and its occurrence in both light waves and sound waves, the correct answer is: (C) both light and Sound waves

Key concepts

Constructive Interference

Constructive interference occurs when two or more waves overlap and their crests (high points) and troughs (low points) align. This results in the waves amplifying each other, creating a wave with larger amplitude. Imagine two ocean waves meeting; if both waves' crests meet at the same time, you get a significantly taller wave.

• In constructive interference, the waves reinforce each other.
• The resulting wave's amplitude is the sum of the individual amplitudes.
• This type of interference can increase the intensity and loudness in sound waves and brightness in light waves.

Recognizing constructive interference is crucial in fields like engineering, music, and optics because it explains why some sounds or lights are naturally more intense.

Destructive Interference

Destructive interference is when waves collide, and their crests and troughs are out of phase. In this case, one wave's crest overlaps with another's trough, resulting in their amplitudes canceling each other out. Think about noise-canceling headphones: they use destructive interference to reduce unwanted sounds.

• With destructive interference, waves diminish each other's strength.
• The resulting wave has a smaller amplitude than the individual waves.
• This effect can lower sound levels or create dark spots in light wave patterns.

Understanding destructive interference helps us manage sound and light effectively, for both privacy and energy efficiency.

Young's Double-Slit Experiment

Young's double-slit experiment is iconic in physics for demonstrating the wave nature of light. In this experiment, coherent light passes through two narrow slits, producing an overlapping pattern of light and dark bands on a screen.

• The light bands result from constructive interference, where the wave peaks align.
• The dark bands are due to destructive interference, where wave peaks and troughs cancel out.
• This experiment helped prove the principle that light behaves like a wave, not just like particles.

Understanding this experiment is vital as it laid the groundwork for modern physics, influencing how we perceive phenomena like diffraction and the behavior of waves at the quantum level.